Sharing USB disks in my Volumio 3 pi 4 with my Mac

I keep a master copy of my Music on a NAS and whenever I add some music, I used to mount the USB in my pi4 on my Mac and then run a disk mirroring program to update the USB in my pi4. I recently upgraded to version 3 and this is the first time I have tried to add a new album in this way. My problem is

My USB disks have strange names (they are called PI4 and RIP)

/dev/sda1       124G   45G   79G  36% /media/49E0-3DB0
/dev/sdb1       251G  161G   90G  65% /media/325D-8B92

and when I browse the disks in the Finder I can see these folder names in the USB directory. The other odd thing is that the modified dates on these folders is 1 Jan 1970.

Any idea how I get the proper names back?

Many thanks